• Journal of Drive and Control
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• v.16 no.4
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• pp.9-15
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• 2019

Bucket trajectory is crucial regarding precision work with an excavator. In general, the bucket trajectory deviation is determined by the machining deviation of the frame, driving deviation of the driving hydraulic cylinder, clearance in the joints, and deformation of the structure. This paper investigated the relationship between the respective clearance in joints and the trajectory deviation of the bucket at the finishing work of the ditching for a 20-ton excavator. As a result, the larger the clearance, the larger deviation is increased at trajectory. However, it was found that the deviation of the rotation angle and displacement of the bucket was limited and the size of clearance does not affect closely on the contact angle of the pin shaft.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.2
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• pp.184-191
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• 2003

A parallel manipulator has high stiffness and all the joint errors on the device are not accumulated at the end -effector unlike a serial manipulator. These are the reasons why the parallel manipulator has been widely used in many fields of industry. In the parallel manipulator, it is very important to predict the exact pose of the end-effector when we want to control the end-effector motion. Installation errors have to be determined in order to predict and control the actual position and pose of the end-effector. This paper presents an algorithm to find the whole 36 joint error components with joint clearance errors and measurement errors considered, when a link length measurement sensor is used and data more than 36 times are acquired for 36 different configurations. A simulation test using this algorithm is performed with a Matlab program which uses the Levenberg-Marquardt method that is known to be efficient for non-linear optimization.

• Journal of Welding and Joining
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• v.18 no.3
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• pp.1-4
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• 2000

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.672-675
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• 2000

There are many sources of errors in the parallel device. This study investigates the effect of a clearance error at a U-joint on the position and orientation errors of the platform of a new parallel device, cubic parallel manipulator. In this study, the limits of errors can be estimated for given conditions.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.6
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• pp.1446-1454
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• 1990

A systematic method of design modification to reduce the influence of impact from multiple clearances in a planar four bar mechanism is developed. For this purpose, an optimization method is used with the objective function which is the linear sum of the Earles and Wu criteria for every joints with clearances. One coil spring is attached to a joint of limited range of revolution to reduce the undesirable dynamic effects due to clearances at joints. The stiffness of the coil spring and its pre-loading angle are chosen as design variables. A numerical example is taken for a four bar mechanism. The initial and modified mechanisms are compared using a clearance mechanism analysis technic to see the difference in dynamic effects due to contact loss. It is found that the modified mechanism produces much more smooth joint contact forces than the original design.

• Journal of Welding and Joining
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• v.19 no.3
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• pp.317-324
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• 2001

This study deals with high power Nd:YAG laser welding of thin steels for small pressure vessels. Full penetration welding at the overlap joint was performed so as to assure sufficient weld strength. Results showed that mid-depth weld size reduced drastically with increasing the travel speed. Position of focus had little effect on the bead formation even though short focal system was used. However, the shape factor and the bead width had closely related with the position of focus. Based on the microstructural inspection, acceptable weld was obtained when the overlap clearance was controlled up to 20% of the base metal thickness. In the case that the joint contained more clearance than the critical value, both the tensile shear strength and the tear strength were reduced. Results also demonstrated that shielding gases were proved to play a key role as far as the bead formation characteristics was taken into consideration. Blowing dry air through 5mm in diameter nozzle produced narrower bead cross-section than that of argon or nitrogen shielding.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.2
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• pp.351-358
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• 1994

A probabilistic model and analysis methods to determine the means and variances of the velocity and acceleration in stochastically-defined planar pin jointed kinematic chains are presented. The presented model considers the effect of tolerances on link length and radial clearance and uncertainty of pin location as a net effect on the link's effective length. The determination of the mean values and variances of the output variables requires the calculation of sensitivities of secondary variables with respect to the random variables. It is shown that this computation is straightforward and can be accomplished by a conventional kinematic analysis package with minor modification. Thus, the concepts of tolerance and clearance have been captured by the model and analysis. The only input data are the nominal linkage model and statistical information. The "effective link length" model is shown to be applicable to both analytical solution and Monte Carlo simulation. The results from both methods are compared. This paper Ksolves the higher-order kinematic problems for the probabilistic design analysis of stochastically-defined mechanisms.echanisms.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.19 no.4
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• pp.12-17
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• 2011

This paper gives a review of finite element model for the analysis of fastening as practical points of view. Different mechanical properties of plate-fastener systems are analyzed. Calculations of the system properties are described as well as the technique of their application in model. Analysis has been performed for calculating the load distribution in multi-joint and the results are compared using the several models. The effects of fastener-hole clearance on the load distribution in multifastener joints are presented. And the stress analysis method have been reviewed for failure analysis of mechanical joint of composite laminate.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.3
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• pp.61-72
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• 1996

In this paper, the driver seat comfort of eight automobiles was studied. The joint angles and anthropometric data of eleven subjects sitting on the seating buck were investigated using the instrument devices such as scale, goniometer, vernier calipers, protractor, Martin set. The joint angles of the most comfort posture were found by experiment and compared with previous studies. The anthropometric data of Korean(1992 year surveys) and American(1970∼1974 year) were applied to evaluate the driver seat layout of Korean automobile. The joint angles of the most comfort posture for eleven subjects were obtained with experimental results. The joint angles were agreed with reference angles. The driver seat layout was not suited to seat length and acceleratorseatpan forward distance in 5 percentiles female, pedal separation and seatpan-roof height in 95 percentiles male. Korean automobiles were not suited to seatpan length and steering wheelseatpan clearance, floor-roof height for American 95 percentiles male. The driver anthropometric dimensions were more suitable to middle size than small size automobiles.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.7
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• pp.643-651
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• 2011

An experimental study on the failure of aluminum sandwich joints under shear loading was conducted. A total of 60 specimens including three different insert types and two different potting types were fabricated and tested. The test results showed that the through-clearance type of joint fails at the highest load among insert type joints. The failure load of the potted joints with the dimple washer increased by 10% compared to the simple potted joints. As expected, the shear failure load became higher in accordance with the face thickness increase. It was also found that the upper face in contact with the loading tool is more dominant over the failure load.